This is not a paid advertisement… I would just like to share the following thrifty-tip. If you want to travel cheaply in Germany, consider traveling with meinfernbus.de .
Instead of paying between 25 and 30 Euros to get from Heidelberg to Frankfurt, or around 100 to get to Hamburg, you can go to Frankfurt for 5 Euros (in 1:50) and Hamburg for 35, right up to the last minute (if you print the ticket yourself).
Otherwise mitfahrgelegenheit (ride-sharing) is always a good cost cutting way to travel, but the relatively new bus-chains in Germany are still quite often cheaper when it comes to going to large cities. And: they have Wifi onboard!